Are Yellowjackets Declining?

By Chris Williams on August 11, 2011.

Q. Yellowjackets are driving us crazy! If we try to eat on the deck, they find us.  They’re chasing the hummingbirds away from the feeders. My son has been stung twice already. How much longer will yellowjackets be active? I’d like my yard back!

A. Unfortunately, late summer is when yellowjackets are most active and most aggressive, but that won’t last much longer. In late summer, a yellowjacket colony is at its largest (1,000-4,000 workers), but its social structure is beginning to break down. At this time of year, there are no more developing larvae to feed so workers are foraging randomly for themselves.

Also in the fall, a yellowjacket’s food interests switch from mainly proteins to mainly sweets which brings them into closer contact with people. They are no longer searching for insects to feed to their larvae. Instead, they are searching for the sugary syrup in the bottom of your soda can. They can become increasingly aggressive in gathering food and are more likely to sting during this time.

waspIn late summer, next year’s queens have developed inside the yellowjacket colony. New males are also produced in the late season colony. The new queens and males leave the nest and mate. Then the newly fertilized queens will look for a protected site, such as under loose tree bark, to spend the winter. Sometimes, the overwintering queens will end up inside buildings seeking shelter.

All of the worker yellowjackets in the colony, along with the current queen, will die at the end of the season. In our region, yellowjacket colonies begin to decline in July or August, but some remain active through September. In cases where the yellowjackets are nesting in voids inside building walls or attics, the nest can remain active well into December. Old yellowjacket nests are not reused the following year. In the spring, a new queen will start a new colony from scratch with the number of workers gradually increasing throughout the summer.



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